Al Gore said on Wednesday it would be "insane, utterly mad and delusional in the extreme" to turn to geo-engineering projects to avoid a climate catastrophe.

The UN climate panel, in the next edition of its blockbuster reports, will warn that governments might have to extract vast amounts of greenhouses gases from the air by 2100 to limit climate change, according to a draft copy of the report seen by Reuters.

But the former vice president of the US said that searches for an instant solution, which he said were born of desperation, were misguided and could lead to an even bigger catastrophe.

"The idea that we can put a different form of pollution into the atmosphere to cancel out the effects of global warming pollution is utterly insane," he told a conference call for South African reporters.

He added: "The fact that some scientists who should know better are actually engaged in serious discussion of those alternatives is a mark of how desperate some of them are feeling due to the paralysis in the global political system."

In March Gore will expand his climate leadership training programmes to South Africa. He said he believed those leadership training sessions (this is his 24th) had developed a cadre of leaders who were helping to find political solutions for climate change.

The draft climate report of the Intergovernmental Panel on Climate Change, due for release in Germany in April, said governments might have to turn increasingly to technologies for "carbon dioxide removal" to keep warming below the dangerous threshold of 2 degrees.

The draft said those technologies might involve capturing and burying emissions from coal-fired power plants, or planting more forests. But there has been debate in the environmental community over other more radical solutions.

On geo-engineering Gore drew a distinction between small-scale interventions, such as white roofs, and large-scale projects meant to extract or neutralise emissions from the air or block the sunlight. Those ideas, he said, carried enormous risks.

"The most discussed so-called geo-engineering proposals – like putting sulphur dioxide in the atmosphere to reflect incoming sunlight – that's just insane. Let's just describe that clearly – it is utterly mad," Gore told the conference call.

He warned that such large and untested experiments carried enormous risks while "doing nothing to address other consequences of climate change such as ocean acidification".

He said: "We are already engaged in a planet-wide experiment with consequences we can already tell are unpleasant for the future of humanity. So the hubris involved in thinking we can come up with a second planet-wide experiment that would exactly counteract the first experiment is delusional in the extreme."

Gore was also cool on the other quick-fix of nuclear power, advocated by some. Late last year four leading US scientists, including the climatologist James Hansen, wrote an open letter urging environmentalists to rethink their opposition to nuclear power.

Gore's re-thinking has apparently gone in the other direction. He told the call he had been an enthusiastic supporter of nuclear energy when he was in Congress. He was not opposed to nuclear energy now, he said. But he said the current state of technology in the nuclear energy industry did not yet warrant a big expansion.

"I do believe that it may be possible for scientists and researchers to develop a better and more inherently safer and cheaper form of nuclear reactor, which may yet play a significant role in resolving this crisis," he told the call. But he added: "It is not available now."

He said he thought such nuclear developments were still 10 or 15 years away. "Unless there are breakthroughs I think the role of nuclear power is likely to be limited to near the level of contribution it is now," he said.